1. Field of the Invention
This invention relates to a camera having a motorized film rewinding device which is arranged to rewind a film with a motor and to automatically bring the operation of the motor to a stop upon completion of film rewinding.
2. Description of the Related Art
Film rewinding can be performed in two different modes. One is a method of taking up the film completely into a film cartridge. The other is a method of incompletely taking up the film into the cartridge leaving a leader part of the film outside of the cartridge. The former film rewinding mode is advantageous with respect to that it readily permits a discrimination between a used roll of film and a new roll of film. However, it is a disadvantage of the former that the film cannot be taken out for a developing process without breaking the cartridge. Meanwhile, it is an advantage of the latter that the film can be readily taken out by just pulling the leader part in developing the film without breaking the cartridge. It is the photographer's liking to make a choice between the two different film rewinding modes.
In a known camera which has been disclosed in Japanese Laid-Open Patent Application No. SHO 57-211131, a switch is arranged in a spool chamber of the camera to be changed from one position over to another according to the presence or absence of the film within the spool chamber and, in carrying out film rewinding with a motor, two different lengths of time after the change-over of the switch position are arranged to be selectable for controlling the end of film rewinding in one of the above-stated two different modes. According to this arrangement, however, in the case of the mode of leaving the leader part of the film outside of the cartridge, there is such a possibility that the photographed frame portions of film might accidentally be pulled out of the cartridge when the back lid of the camera is opened for taking out the cartridge from the camera in the event of incomplete disengagement of a sprocket from the perforation of the leader part of film. In the worst possible case, all the frame positions of film might be exposed to light with the cartridge dropped off the camera leaving the leader part perforation in a state of engaging the sprocket.
Further, in the conventional camera of the kind arranged to have the film movement monitored by detection means for automatically bringing a motor to a stop upon completion of film rewinding with the motor and to have the driving action of the motor automatically brought to a stop in case that the output state of the detection means fails to come to change after the lapse of a given period of time set by a timer, the film must be firmly and tightly wound round a take-up reel disposed within the cartridge. If not, when the film is rewound after photographing for a number of frames less than the total number of photographable frame portions of the film; a predetermined timer time might be wasted while a coiled part of the film tightens within the cartridge and then the motor might automatically come to a stop before the film is adequately rewound. This trouble often happens particularly in the case of 12- or 24-exposure film products.
On the other hand, Japanese Laid-Open Patent Application No. SHO 60-52834 has disclosed a camera which is arranged to have a relatively long timer time to sufficiently allow a film coil to tighten before the film begins to move and to change the long timer time over to a relatively short timer time when the film begins to move, so that completion of film rewinding can be detected in a short period of time.
Meanwhile, there is the desire to have the film incompletely rewound into the cartridge leaving the leader part of film left outside the cartridge, because it facilitates developing work when the work is to be done by the photographer.
It may appear to be possible to meet this requirement by the camera proposed in the above-stated Japanese laid-open patent application to public inspection by adjusting the above-stated relatively short timer time after commencement of film movement to such a length of time that enables the leader part of film to completely disengage a sprocket provided with film movement detecting means but not to be pulled into the cartridge. However, unstable acceleration of film movement at the build-up of the film rewinding process results in a variable length of time before stabilization of the film moving speed. The output state of the detecting means, therefore, might stay unchanged under the low speed condition before the stabilization of speed while the timer time is lapsing. In that event, the film winding action automatically comes to a stop when only a portion of the film is rewound.